Several approaches have been taken in an attempt to deliver genes to humans for therapeutic purposes. In one approach, lymphocytes have been removed and permanently transformed in vitro using virus vectors. The lymphocytes have been reinfused as transformed cells. Alternatively, adenoviruses have been used to deliver a gene by the air ways of an animal, again using retrovirus vectors.
The present invention utilizes a unique plasmid for gene therapy. By way of background, a plasmid is a circular piece of DNA which can function to express genes (pieces of DNA) which have been inserted into the plasmid. Copending applications U.S. Ser. No. 678,027, filed Apr. 1, 1991, now abandoned and U.S. Ser. No. 690,283, filed Apr. 24, 1991, now abandoned disclose plasmids consisting essentially of a small pCMV4 expression vector including a specific coding sequence. Both prior art patents relate to the complexing of these plasmids with liposomes for delivery of the gene to a patient. The liposome includes or is complexed with the expression plasmid incorporated therein, the plasmid being capable of expression extrachromosomally in the cells of a target tissue and being unincorporable into the chromosome of the cells of the target tissue. These plasmids provide a means of treatment for deficiency of a gene product in cells of a target tissue.
Prostaglandin synthase is the proximal enzyme in the conversion of arachidonic acid to several prostanoids. Prostanoids are normally produced ubiquitously in the body and include several highly bioactive substances that are felt to be important in homeostasis. The endothelial prostanoids, prostacyclin and prostaglandin E.sub.2 (PGE.sub.2) are especially important as these prostanoids have several properties which could be important in preventing or curing disease.
For example, prostacyclin prevents aggregation of platelets, an initial event in clotting in blood vessels. It has been hypothesized that the generation of prostacyclin by the cells lining the blood vessels is necessary and important to prevent clotting under normal circumstances. It is further felt that increased amounts of prostacyclin, particularly in a localized area, can prevent the propagation of clots in small blood vessels as may occur in pulmonary embolus or myocardial infarction. PGE.sub.2 is also produced especially by microvascular endothelial cells. PGE.sub.2 dilates systemic blood vessels and also inhibits the generation of several cytokines which may be responsible for several of the physiologic and structural consequences of inflammation. If endothelial cells or perhaps other cells in the body can be engineered to produce increased amounts of these protective prostanoids, the result can be therapeutic in a variety of human diseases. Such diseases would include, in addition to pulmonary embolus and myocardial infarction, several diseases of the lungs.
Experimental evidence indicates that prostacyclin and PGE.sub.2 may protect the lungs from injury by endotoxin, such as occurs in the clinical syndrome called adult respiratory distress syndrome (ARDS) Brigham et al., Prostaglandin E.sub.2 attenuation of sheep lung responses to endotoxin., J. Appl. Physiol 64:2568 (1988). Prostacyclin dilates blood vessels in the lung and has been used in therapeutic trials in the treatment of primary pulmonary hypertension, a disease for which there is no acceptable treatment at the present time. Robin, L., Clin. Pulmonary Circ. In Health and Disease; Will, Davison, Weir and Buebrier, eds. Acad. Press, N.Y. pp 491-498 (1987). Prostanoids also dilate airway smooth muscle and therefore could be therapeutic in asthma.
The present invention provides a means for producing hyperexpression of the prostaglandin synthase gene thereby resulting in hyperproduction of prostanoids in cells proximate to an area in which such increases might be beneficial.